However this only underscores the fundamental problem with OpenPGP: relatively few people use it and only a fraction of them are connected into the strong set. This is in part a bootstrapping problem. With the web of trust connecting so few people it is hard to find someone to sign your key and key signing parties are a fair amount of work to organize.

So my idea to help OpenPGP users connect: a mobile phone app that tells you when you are close to a fellow user with whom you have not exchanged signatures.

Features

Authentication either with the key or (for those who don't want to keep their key on their phone) by a signed token.